implement delete, new js client

I implemented delete with class Deletion, renaming previous class Change to Insertion.
I implemented a new js client whose test page is available at localhost:3000/new#username with:
- insertion
- deletion (both del and backspace)
- arrow keys navigation
- disabled enter key
New implementation is missing sidebar features (chat messages and control), uses the url hash to set username and has an hardcoded filename 'a'.
Tired of waiting for the js libraries to download from CDNs I downloaded them and made available locally.
I just updated the old js client so that it uses Insertion instead of Change and local js libraries.
Hope you like it ;)

	new file:   app/js/jquery-1.9.1.min.js